A new theory about the development of secondary caries

Introduction: Secondary caries is considered to start at the outer surface of the tooth adjacent to a restoration in presence of an active biofilm. A carious lesion along the dentin-enamel junction (DEJ) detected after removal of a restoration is considered to be ‘residual' caries (Mjör et al., 2000; Kidd, 2001). In this study it is hypothesized that cusp-movement during loading induces percolation and microleakage in absence of a biofilm with secondary caries at the DEJ as a result. The presence of a crack visible after removal of a restoration facilitates percolation.

Objectives. To evaluate the relation between the presence of cracks and carious lesions along the dentin-enamel junction in teeth with an amalgam restorations.

Methods: Premolar and molar teeth needing replacement of Class I and II amalgam restorations were included in this study. Exclusion criteria were teeth with restorations with marginal fractures, visible marginal cavitation (indicating presence of a carious lesion) or caries detected on a radiograph. In 99 teeth amalgam restorations were carefully removed including the corrosion products before cavity walls were visually inspected for the presence of caries at the DEJ and cracks in cusps. Data were statistically analyzed using a Chi-square test at p<0.05.

Results: Statistical analysis revealed a significant effect of the presence of cracks and the presence of caries along the DEJ (p<0.001).  

Conclusion: The outcome of the study suggests that in the development of secondary caries percolation due to the presence of cracks plays an important role.